Objective To investigate the pathogenesis of deep vein thrombosis (DVT) after total hip arthroplasty (THA) and the preventive effectiveness of low molecular weight heparin (LMWH). Methods The occurrence condition of DVT in 90 cases undergoing THA treated with LMWH between February 2003 and March 2004 was restrospectively analyzed. Among 90 cases, 39 were treated with LMWH at a dose of 5 000 U/day (high dose group) and 51 at a dose of 2 500 U/day (low dose group). Another 90 cases undergoing THA without LMWH treating between February 2002 and February 2003 were used as control group. There was no significant difference in gender, age, illness cause, course of disease, or the type of prosthesis among 3 groups (P gt; 0.05). Results DVT occurred in 19 cases (21.1%) of control group, in 2 cases (5.1%) of high dose group, and in 5cases (9.8%) of low dose group, showing significant differences between two treated groups and control group (P lt; 0.05), but no significant difference between two treated groups (P gt; 0.05). There was no significant difference in gender, age (gt; 65 years and ≤ 65 years), pathogen (trauma and bone disease) of each group, as well as of the same type patients within 3 groups (P gt; 0.05). The DVT incidence rate in the patients with bone cement artificial joint was significantly higher than that in the patients with non-bone cement artificial joint (P lt; 0.05), but there was no significant difference in the same type patients within 3 groups (P gt; 0.05). The postoperative blood loss in high dose group, low dose group, and control group was (463.5 ± 234.2), (342.4 ± 231.6), and (288.2 ± 141.6) mL; showing no significant difference between the high and low dose groups, between low dose and control groups (P gt; 0.05), while showing significant difference between high dose and control groups (P lt; 0.05). Conclusion The DVT incidence rate in THA patients with bone cement artificial joint is high; LMWH can reduce the DVT incidence rate and has good safety.